Glass ceramics, chemically strengthened glass, and semiconductor substrate

ABSTRACT

The present invention relates to a glass ceramic having a visible-light transmittance of 85% or more in terms of a thickness of 0.7 mm, and a haze value of 1.0% or less in terms of a thickness of 0.7 mm, and including, in mass % on an oxide basis: 45-70% of SiO2; 1-15% of Al2O3; and 10-25% of Li2O.

TECHNICAL FIELD

The present invention relates to glass ceramics, chemically strengthenedglass, and a semiconductor-supporting substrate.

BACKGROUND ART

Chemically strengthened glasses are used as the cover glasses ofportable digital assistances, etc.

A chemically strengthened glass is obtained, for example, by bringing aglass into contact with a molten salt which contains alkali metal ionsand causing ion exchange between alkali metal ions contained in theglass and alkali metal ions contained in the molten salt to form acompressive stress layer in the glass surface.

Glass ceramics are obtained by precipitating crystals in a glass, and isharder and less apt to receive scratches as compared with amorphousglasses containing no crystals. Patent Literature 1 presents an examplein which glass ceramics were chemically strengthened by ion exchangetreatment. However, glass ceramics are inferior to amorphous glasses intransparency.

Patent Literature 2 describes transparent glass ceramics. However, thereare few transparent glass ceramics having high transparency whichrenders the glass ceramics suitable for use as cover glasses. Thechemical strengthening properties of glass ceramics are greatly affectedby the glass composition and the precipitated crystals. The scratchresistance and transparency of the glass ceramics are also greatlyaffected by the glass composition and the precipitated crystals. It ishence necessary to delicately regulate a glass composition andprecipitated crystals, for obtaining glass ceramics excellent in termsof both chemical strengthening property and transparency.

Meanwhile, in the field of semiconductor packaging, techniques such aswafer-level packaging (WLP) or panel-level packaging (PLP) are receivingattention (see Patent Literature 2). These techniques are, for example,a technique in which silicon chips are placed on a glass substrate andencapsulated by molding an encapsulating resin.

In this technique, there are cases where the supporting substrate isremoved during the production. Widely used as the supporting substrateare glass substrates. Since the glass substrates are transparent, theycan be made removable by irradiation with laser light. The glasssubstrates for use as supporting substrates are required to be less aptto be damaged in the packaging step, not to scatter fragments uponbreakage, and to match in thermal expansion with the semiconductors.

CITATION LIST Patent Literature

Patent Literature 1: JP-T-2016-529201 (The term “JP-T” as used hereinmeans a published Japanese translation of a PCT patent application.)

Patent Literature 2: JP-A-2016-160136

SUMMARY OF INVENTION Technical Problem

The present invention provides a glass ceramic excellent in terms oftransparency and chemical strengthening property. The present inventionfurther provides a chemically strengthened glass which has a highthermal expansion coefficient, is excellent in terms of transparency andstrength, and is less apt to scatter fragments upon breakage.

Solution to Problem

The present invention provides a glass ceramic having a visible-lighttransmittance of 85% or more in terms of a thickness of 0.7 mm, and ahaze value of 1.0% or less in terms of a thickness of 0.7 mm, and

including, in mass % on an oxide basis:

45-70% of SiO₂;

1-15% of Al₂O₃; and

10-25% of Li₂O.

The present invention further provides a chemically strengthened glasshaving a compressive stress layer in a surface thereof, the chemicallystrengthened glass being a glass ceramic that has a visible-lighttransmittance of 85% or more in terms of a thickness of 0.7 mm, and ahaze value of 0.5% or less in terms of a thickness of 0.7 mm,

has a surface compressive stress value of 500 MPa or more and a depth ofthe compressive stress layer of 80 μm or more, and

includes, in mass % on an oxide basis:

45-70% of SiO₂;

1-15% of AlO₃; and

10-25% of Li₂O.

The present invention further provides a semiconductor-supportingsubstrate including the glass ceramic or the chemically strengthenedglass.

Advantageous Effects of Invention

According to the present invention, a glass ceramic excellent in termsof transparency and chemical strengthening property is obtained.Furthermore, a chemically strengthened glass which has a high thermalexpansion coefficient, is excellent in terms of transparency andstrength, and is less apt to scatter fragments upon breakage isobtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating one example of stress profiles of achemically strengthened glass.

FIG. 2 is a diagram illustrating one example of powder X-ray diffractionpatterns of a glass ceramic.

FIG. 3 is a diagram illustrating one example of powder X-ray diffractionpatterns of another glass ceramic.

FIG. 4 is a diagram illustrating one example of DSC curves of anamorphous glass according to the present invention.

FIG. 5A and FIG. 5B illustrate a supporting glass according to oneembodiment of the present invention which is for laminating with asemiconductor substrate; FIG. 5A is a cross-sectional view showing thesupporting glass which has not been laminated; and FIG. 5B is across-sectional view showing the supporting glass which has beenlaminated.

FIG. 6 is a cross-sectional view of a laminated substrate according toone embodiment of the present invention.

FIG. 7 is a drawing showing one example of TEM images of a glassceramic.

DESCRIPTION OF EMBODIMENTS

In this description, “-” indicating a numerical range is used in thesense of including the numerical values set forth before and after the“-” as a lower limit value and an upper limit value unless otherwiseindicated.

In this description, “amorphous glass” and “glass ceramic” arecollectively referred to as “glass”. In this description, the term“amorphous glass” means a glass in which no diffraction peak indicatingcrystals is observed by a powder X-ray diffraction method. A “glassceramic” is a glass obtained by heating an “amorphous glass” toprecipitate crystals therein, and contains the crystals.

In an examination by powder X-ray diffractometry, a sample is examinedusing CuKα ray in the 20 range of 10°-80°; in cases when diffractionpeaks have appeared, the precipitated crystals are identified by, forexample, a Hanawalt method.

Hereinafter, the term “chemically strengthened glass” means a glasshaving undergone a chemical strengthening treatment, and the term “glassfor chemical strengthening” means a glass before being subjected to achemical strengthening treatment.

The “base composition of a chemically strengthened glass” is the glasscomposition of the glass for chemical strengthening. Except for the casewhere an immoderate ion exchange treatment has been performed, the glasscomposition of any portion of the chemically strengthened glass whichlies deeper than a depth of compressive stress layer DOL is the basecomposition of the chemically strengthened glass.

In this description, glass composition is expressed in mass % on anoxide basis unless otherwise indicated, and “mass %” is simply writtenas “%”.

In this description, the expression “substantially contain no” meansthat the content is not higher than a level of impurities contained inraw materials or the like, i.e., the substance has not beenintentionally added. Specifically, the content is, for example, lessthan 0.10%.

In this description, the term “stress profile” means a profile showingcompressive stress values using the depth from a glass surface as avariable. An example is shown in FIG. 1. In the stress profile, tensilestress is expressed as negative compressive stress.

“Compressive stress value (CS)” can be determined by forming a thinsection of the glass and analyzing the thin-section sample by abirefringence imaging system. The birefringence imaging systembirefringence stress meter is a device for measuring the magnitude ofany retardation caused by stress by using a polarization microscope, aliquid-crystal compensator, etc. An example thereof is birefringenceimaging system Abrio-IM, manufactured by CRi, Inc.

There are cases where CS values can be determined by utilizingscattered-light photoelasticity. In this method, light is caused toenter the glass through a surface thereof and the resultant scatteredlight is analyzed for polarization, thereby determining the CS. Examplesof stress meters in which scattered-light photoelasticity is utilizedinclude scattered-light photoelastic stress meters SLP-1000 andSLP-2000, manufactured by Orihara Manufacturing Co., Ltd.

In this description, “depth of compressive stress layer (DOL)” is adepth at which the compressive stress value becomes zero. Hereinafter,surface compressive stress value is sometimes denoted by CS₀ andcompressive stress value at a depth of 50 m is sometimes denoted byCS₅₀. The term “internal tensile stress (CT)” means a tensile stressvalue at a depth corresponding to ½ of a sheet thickness t.

In this description, the term “light transmittance” means an averagelight transmittance of light having wavelengths ranging from 380 nm to780 nm. The term “haze value” is measured using a C illuminant inaccordance with JIS K3761:2000.

In this description, the color of glass ceramic is a color determinedfrom a transmission spectrum of a 0.7-mm-thick sample of the glassceramic sheet under C illuminant. The color is expressed using eithertristimulus values X, Y, and Z according to the XYZ color system definedby JIS Z8701:1999 and the appendix thereof or a main wavelength Md andan excitation purity Pe which are calculated from those values.

In this description, the term “Vickers hardness” means the Vickershardness (HV0.1) defined in JIS R1610:2003.

“Fracture toughness value” can be measured using a DCDC method (Actametall. mater., Vol. 43, pp. 3453-3458, 1995).

In this description, the term “semiconductor” means not only asemiconductor wafer of silicon, etc., or a semiconductor chip, but alsosometimes a composite structure including a chip, a wiring layer, and amold resin.

<Glass Ceramic>

From the standpoint of enabling a remarkable improvement in strength bychemical strengthening, a thickness (t) of the present glass ceramic ispreferably 3 mm or less, and is more preferably 2 mm or less, 1.6 mm orless, 1.1 mm or less, 0.9 mm or less, 0.8 mm or less, and 0.7 mm or lessstepwisely. From the standpoint of obtaining sufficient strength througha chemical strengthening treatment, the thickness (t) is preferably 0.3mm or more, more preferably 0.4 mm or more, still more preferably 0.5 mmor more.

Since the present glass ceramic has a light transmittance of 85% or morewhen having a thickness of 0.7 mm, use of the present glass ceramic asthe cover glasses of portable displays renders images on the displayscreens easy to see. The light transmittance is preferably 88% or more,more preferably 90% or more. The higher the light transmittance, themore preferred. Usually, however, the light transmittance is 91% orless. The transmittance of 90% is comparable to that of ordinaryamorphous glasses.

The haze value, in the case where the thickness is 0.7 mm, is 1.0% orless, and is preferably 0.4% or less, more preferably 0.3% or less,still more preferably 0.2% or less, especially preferably 0.15% or less.The smaller the haze value, the more preferred. However, if the degreeof crystallinity or the crystal-particle size is reduced in order toreduce a haze value, this results in a decrease in mechanical strength.From the standpoint of attaining high mechanical strength, the hazevalue in the case of a thickness of 0.7 mm is preferably 0.02% or more,more preferably 0.03% or more.

The present glass ceramic has a Y value according to the XYZ colorsystem of preferably 87 or more, more preferably 88 or more, still morepreferably 89 or more, especially preferably 90 or more. For use ascover glasses for portable displays, it is preferable that thecoloration of the glass itself is as little as possible, from thestandpoint of heightening the displayed-color reproducibility in thecase of using the glass ceramic on the display screen side or from thestandpoint of maintaining design attractiveness in the case of using theglass ceramic on the housing side. The present glass ceramic hence hasan excitation purity Pe of preferably 1.0 or less, more preferably 0.75or less, still more preferably 0.5 or less, especially preferably 0.35or less, most preferably 0.25 or less.

In the case where the present glass ceramic or a strengthened glassobtained by strengthening the glass ceramic is for use as a cover glassof a portable display, it is preferable that this glass gives a textureand a sense of high quality different from plastics. From thisstandpoint, the present glass ceramic has a main wavelength λd ofpreferably 580 nm or less and a refractive index of preferably 1.52 ormore, more preferably 1.55 or more, still more preferably 1.57 or more.

The present glass ceramic is preferably a glass ceramic containinglithium metasilicate crystals. Lithium metasilicate crystals areexpressed by Li₂SiO₃ and are crystals generally giving a powder X-raydiffraction spectrum having diffraction peaks at Bragg angles (2θ) ofabout 26.98°, 18.88°, and 33.05°. FIG. 2 shows an example of X-raydiffraction spectra of the present glass ceramic, in which lithiummetasilicate crystals are observed.

It is also preferable that the present glass ceramic is a glass ceramiccontaining lithiumphosphate crystals. Lithiumphosphate crystals areexpressed by Li₃PO₄ and are crystals giving a powder X-ray diffractionspectrum having diffraction peaks at Bragg angles (2°) of about 22.33°,23.18°, and 33.93°. FIG. 3 shows an example of powder X-ray diffractionspectra of the present glass ceramic, in which lithium metasilicatecrystals and lithiumphosphate crystals are clearly observed. Acomparison between FIG. 2 and FIG. 3 indicates that the glass ceramic ofFIG. 2 also contains lithiumphosphate crystals. The precipitation oflithiumphosphate crystals tends to enhance the chemical durability.

The present glass ceramic may contain both lithium metasilicate crystalsand lithiumphosphate crystals.

The present glass ceramic is obtained by heating and crystallizing anamorphous glass which will be described later.

The glass ceramic containing lithium metasilicate crystals has a higherfracture toughness value than usual amorphous glasses and is less apt tosuffer an intense fracture even when high compressive stress is providedby chemical strengthening. There are cases where, in an amorphous glassin which lithium metasilicate crystals can be precipitated, theprecipitation of lithium disilicate occurs depending on heat-treatmentconditions, etc. Lithium disilicate is expressed by Li₂Si₂O₅ and iscrystals generally giving a powder X-ray diffraction spectrum havingdiffraction peaks at Bragg angles (2θ) of about 24.89°, 23.85°, and24.40°.

In the case where the glass ceramic contains lithium disilicatecrystals, it is preferable that the lithium disilicate crystals have aparticle size (referred to also as crystal size) of 45 nm or less, theparticle size being determined using a Scherrer equation from the widthsof X-ray diffraction peaks. This is because transparency is apt to beobtained with such lithium disilicate crystals. The particle sizethereof is more preferably 40 nm or less.

However, in cases when lithium metasilicate crystals and lithiumdisilicate crystals are simultaneously contained in a glass ceramic,this glass ceramic is prone to have reduced transparency. It is hencepreferable that the present glass ceramic does not contain lithiumdisilicate. The expression “does not contain lithium disilicate” meansthat the glass ceramic gives an X-ray diffraction spectrum in which nodiffraction peak of lithium disilicate crystals is detected.

The present glass ceramic has a degree of crystallinity of preferably 5%or more, more preferably 10% or more, still more preferably 15% or more,especially preferably 20% or more, from the standpoint of heighteningthe mechanical strength. From the standpoint of heightening thetransparency, the degree of crystallinity thereof is preferably 70% orless, more preferably 60% or less, especially preferably 50% or less.The glass ceramic having a low degree of crystallinity is superior inthat this glass is easy to be subjected to bending formation, etc. byheating. The term “degree of crystallinity” as used herein, for example,a degree of crystallinity of a glass ceramic in which lithiummetasilicate crystals and lithiumphosphate crystals have beenprecipitated means a degree of crystallinity for both the lithiummetasilicate crystals and the lithiumphosphate crystals.

The degree of crystallinity can be calculated from X-ray diffractionintensity by a Rietveld method. The Rietveld method is described in“Handbook of Crystal Analysis” edited by the “Handbook of CrystalAnalysis” Editing Committee of the Crystallographic Society of Japan(published by Kyoritsu Shuppan Co., Ltd., 1999, pp. 492-499).

The average particle size of the precipitated crystals in the presentglass ceramic is preferably 80 nm or less, more preferably 60 nm orless, still more preferably 50 nm or less, especially preferably 40 nmor less, most preferably 30 nm or less. The average particle size ofprecipitated crystals is determined from images obtained with atransmission electron microscope (TEM). The average particle size ofprecipitated crystals can be estimated from images obtained with ascanning electron microscope (SEM).

The present glass ceramic has an average thermal expansion coefficientat 50-350° C. of preferably 90×10⁻⁷/C or more, more preferably100×10⁻⁷/° C. or more, still more preferably 110×10⁻⁷/° C. or more,especially preferably 120×10⁻⁷/° C. or more, most preferably 130×10⁻⁷/°C. or more.

In case where the thermal expansion coefficient is too high, there is apossibility that this glass might crack due to a difference in thermalexpansion during chemical strengthening. The average thermal expansioncoefficient is hence preferably 160×10⁻⁷/° C. or less, more preferably150×10⁻⁷/° C. or less, still more preferably 140×10⁻⁷/° C. or less.

The glass ceramic having such a thermal expansion coefficient issuitable for use as a supporting substrate for semiconductor packagesincluding resin components in large proportions.

The present glass ceramic has a high hardness since it containscrystals. Because of this, the glass ceramic is less apt to receivescratches and has excellent wear resistance. The Vickers hardnessthereof is preferably 600 or more, more preferably 700 or more, stillmore preferably 730 or more, especially preferably 750 or more, mostpreferably 780 or more, from the standpoint of enhancing the wearresistance.

Too high hardness result in poor workability. The Vickers hardness ofthe present glass ceramic is hence preferably 1,100 or less, morepreferably 1,050 or less, still more preferably 1,000 or less.

The present glass ceramic has a Young's modulus of preferably 85 GPa ormore, more preferably 90 GPa or more, still more preferably 95 GPa ormore, especially preferably 100 GPa or more, from the standpoint ofinhibiting strengthening warpage during chemical strengthening. Thereare cases where the present glass ceramic is polished before being used.From the standpoint of facilitating polishing, the Young's modulusthereof is preferably 130 GPa or less, more preferably 125 GPa or less,still more preferably 120 GPa or less.

The present glass ceramic has a fracture toughness value of 0.8MPa·m^(1/2) or more, more preferably 0.85 MPa·m^(1/2) or more, stillmore preferably 0.9 MPa·m^(1/2) or more. This is because the glassceramic having such a fracture toughness value, after having beenchemically strengthened, is less apt to scatter fragments upon breakage.

The present glass ceramic preferably has a relative permittivity P of8.0 or less at a frequency of 10 GHz. This is because the glass ceramichaving such a relative permittivity brings about satisfactorycommunication efficiency when used in radio communication appliances forhigh-frequency communication. The relative permittivity F of the presentglass ceramic at a frequency of 10 GHz is more preferably 7.6 or less,still more preferably 7.3 or less. The F thereof is usually 3.7 or more.

The present glass ceramic has a lower dielectric loss tangent tan δ at afrequency of 10 GHz than the glass which has not undergonecrystallization; the present glass ceramic is hence preferred. Thereduced dielectric loss tangent is owing to the fact that crystalshaving a lower tan δ than the glass have precipitated in the glass andthis precipitation has reduced the tan δ of the glass as a whole. Thetan δ thereof is preferably 0.014 or less because the present glassceramic having such a value of tan δ brings about satisfactorycommunication efficiency when used in radio communication appliances forhigh-frequency communication. The dielectric loss tangent tan δ of thepresent glass ceramic at a frequency of 10 GHz is more preferably 0.012or less, still more preferably 0.010 or less, yet still more preferably0.008 or less. The tan δ thereof is usually 0.002 or more.

The present glass ceramic has the same glass composition as theamorphous glass which has not undergone crystallization yet, and thusthe glass composition thereof will be explained later in the section“Amorphous Glass”.

<Chemically Strengthened Glass>

The chemically strengthened glass (hereinafter sometimes referred to as“the present strengthened glass”) obtained by chemically strengtheningthe present glass ceramic preferably has a surface compressive stressvalue CS₀ of 600 MPa or more. This is because the present strengthenedglass having such a surface compressive stress value is less apt tocrack when deformed by deflection, etc. The surface compressive stressvalue of the present strengthened glass is more preferably 800 MPa ormore.

The present strengthened glass has a depth of compressive stress layerDOL of preferably 80 μm or more. This is because the strengthened glassis less apt to crack even when a surface thereof receives scratches. TheDOL thereof is preferably 100 m or more.

The larger the compressive stress value CS₅₀ at a depth of compressivestress layer of 50 μm, the higher the strength in thedrop-onto-sandpaper test shown below, i.e., drop strength. The CS₅₀thereof is preferably 80 MPa or more, more preferably 100 MPa or more,still more preferably 120 MPa or more, especially preferably 140 MPa ormore.

(Drop-onto-Sandpaper Test)

A glass sheet (120 mm×60 mm×0.7 mm) to be evaluated is taken as a coverglass for a smartphone and attached to a housing as an imitation of thesmartphone, and this assembly is dropped onto the surface of flat SiC#180 sandpaper. The total mass of the glass sheet and the housing isadjusted to about 140 g.

The test is initiated with a height of 30 cm, and in cases when thechemically strengthened glass sheet has not cracked, this assembly isthen dropped from a height increased by 10 cm. The dropping is thusrepeated and the height [unit: cm] which has resulted in cracking isrecorded. This test as one set is repeated to conduct 10 sets, and anaverage of the heights which have resulted in cracking is taken as “dropheight”.

The present strengthened glass preferably has a drop height in thedrop-onto-sandpaper test of 80 cm or more.

It is preferable that the present strengthened glass has an internaltensile stress (CT) of 110 MPa or less, because this chemicallystrengthened glass having such a CT is inhibited from scatteringfragments upon breakage. The CT thereof is more preferably 100 MPa orless, still more preferably 90 MPa or less. Meanwhile, a reduction in CTtends to reduce the surface compressive stress, making it difficult toobtain sufficient strength. Consequently, the CT thereof is preferably50 MPa or more, more preferably 55 MPa or more, still more preferably 60MPa or more.

The present strengthened glass has a four-point bending strength ofpreferably 500 MPa or more, more preferably 550 MPa or more, still morepreferably 600 MPa or more. The four-point bending strength is measuredusing a test piece of 40 mm×5 mm×0.8 mm under the conditions of a lowerspan of 30 mm, an upper span of 10 mm, and a cross head speed of 0.5mm/min. An average value for 10 test pieces is taken as the four-pointbending strength.

A higher Vickers hardness of the present strengthened glass tends tobecome higher than the unstrengthened glass, through the chemicalstrengthening treatment. This is thought to be because the ion exchangebetween small ions in crystals and large ions in the molten salt hasproduced compressive stress in the crystals.

The Vickers hardness of the present strengthened glass is preferably 720or more, more preferably 740 or more, still more preferably 780 or more.The Vickers hardness of the present strengthened glass is usually 950 orless.

In general, the glass transition points of glass ceramics are higherthan the glass transition points of amorphous glasses having the sameglass composition. From the standpoint of inhibiting stress relaxationfrom occurring during chemical strengthening treatments, the glasstransition point of the glass ceramic is preferably 500° C. or more,more preferably 530° C. or more, still more preferably 550° C. or more,especially preferably 570° C. or more. From the standpoint of subjectingthe glass ceramic to, for example, bending with heating, the glasstransition point of the glass ceramic is preferably 850° C. or less,more preferably 800° C. or less, still more preferably 750° C. or less,especially preferably 700° C. or less.

The difference ΔTg between the glass transition point of the presentglass ceramic and the glass transition point of an amorphous glasshaving the same glass composition is preferably 200° C. or less, morepreferably 195° C. or less, still more preferably 190° C. or less. Glassceramics having a small ΔTg are easy to process by, for example, bendingwith heating.

The present strengthened glass has the same visible-light transmittance,haze value, and high-frequency characteristics as the present glassceramic. Explanations thereon are hence omitted.

The present strengthened glass as a whole has approximately the samecomposition as the glass ceramic which has not been strengthened, exceptfor the case where the strengthened glass has undergone an immoderateion exchange treatment. In particular, the portion lying most deeplyfrom the glass surfaces has the same composition as the glass ceramicwhich has not been strengthened, except for the case where thestrengthened glass has undergone an immoderate ion exchange treatment.

<Amorphous Glass>

The amorphous glass according to the present invention preferablyincludes, in mass % on an oxide basis, 45-70% of SiO₂, 1-15% of Al₂O₃,10-25% of Li₂O, 0-12% of P₂O₅, 0-15% of ZrO₂, 0-10% of Na₂O, 0-5% ofK₂O, and 0-6% of Y₂O₃.

This glass composition is explained below.

In the present amorphous glass, SiO₂ is a component forming a networkstructure of the glass. In addition, SiO₂ is a component enhancing thechemical durability and is a constituent component of lithiummetasilicate as precipitated crystals. The content of SiO₂ is preferably45% or more. The content of SiO₂ is more preferably 48% or more, stillmore preferably 50% or more, especially preferably 52% or more,extremely preferably 54% or more. Meanwhile, from the standpoint ofenhancing meltability, the content of SiO₂ is preferably 70% or less,more preferably 68% or less, still more preferably 66% or less,especially preferably 64% or less.

Al₂O₃ is a component increasing the surface compressive stress to begenerated by chemical strengthening, and is essential. The content ofAl₂O₃ is preferably 1% or more. The content of Al₂O₃ is more preferably2% or more, still more preferably 4% or more, especially preferably 6%or more, extremely preferably 8% or more. Meanwhile, from the standpointof preventing the glass from having too high a devitrificationtemperature, the content of Al₂O₃ is preferably 15% or less, morepreferably 12% or less, still more preferably 10% or less, especiallypreferably 8% or less, most preferably 6% or less.

Li₂O is a component forming surface compressive stress through ionexchange, is a constituent component of lithium metasilicate crystals,and is essential. The content of Li₂O is preferably 10% or more, morepreferably 14% or more, still more preferably 16% or more, especiallypreferably 18% or more. Meanwhile, from the standpoint of stabilizingthe glass, the content of Li₂O is preferably 25% or less, morepreferably 22% or less, still more preferably 20% or less.

Na₂O is a component improving the meltability of the glass. AlthoughNa₂O is not essential, the content thereof is preferably 0.5% or more,more preferably 1% or more, especially preferably 2% or more. In casewhere the content of Na₂O is too high, lithium metasilicate crystals areless apt to be precipitated or the glass has a reduced chemicalstrengthening property. The content of Na₂O hence is preferably 10% orless, more preferably 9% or less, still more preferably 8% or less,especially preferably 7% or less.

K₂O is a component lowering the melting temperature of the glass likeNa₂O, and may be contained. In cases when K₂O is contained, the contentthereof is preferably 0.5% or more, more preferably 1% or more, stillmore preferably 1.5% or more, especially preferably 2% or more. Too highK₂O contents result in a decrease in chemical strengthening property ora decrease in chemical durability. The content of K₂O hence ispreferably 5% or less, more preferably 4% or less, still more preferably3% or less, especially preferably 2% or less.

The total content of Na₂O and K₂O, i.e., Na₂O+K₂O, is preferably 1% ormore, more preferably 2% or more.

In cases when the sum of Li₂O, Na₂O, and K₂O, i.e., Li₂O+Na₂O+K₂O, isexpressed by R₂O, it is preferable that K₂O/R₂O is 0.2 or less. This isbecause such value of the ratio can enhance the chemical strengtheningproperties and heighten the chemical durability. That ratio is morepreferably 0.15 or less, still more preferably 0.10 or less.

R₂O is 10% or more, preferably 15% or more, more preferably 20% or more.Meanwhile, R₂O is 29% or less, preferably 26% or less.

P₂O₅, although not essential, has the effect of promoting phaseseparation in the glass to accelerate crystallization and may becontained. In cases when P₂O₅ is contained, the content thereof ispreferably 0.5% or more, more preferably 2% or more, still morepreferably 4% or more, especially preferably 5% or more, extremelypreferably 6% or more. Meanwhile, too high P₂O₅ contents not only makethe glass prone to undergo phase separation during melting but alsoresult in a considerable decrease in acid resistance. The content ofP₂O₅ is preferably 12% or less, more preferably 10% or less, still morepreferably 8% or less, especially preferably 7% or less.

ZrO₂ is a component capable of constituting crystal nuclei in acrystallization treatment and may be contained. The content of ZrO₂ ispreferably 1% or more, more preferably 2% or more, still more preferably4% or more, especially preferably 6% or more, most preferably 7% ormore. Meanwhile, from the standpoint of inhibiting devitrificationduring melting, the content of ZrO₂ is preferably 15% or less, morepreferably 14% or less, still more preferably 12% or less, especiallypreferably 11% or less.

In cases when the sum of Li₂O, Na₂O, and K₂O, i.e., Li₂O+Na₂O+K₂O, isexpressed by R₂O, then ZrO₂/R₂O is preferably 0.10 or more, morepreferably 0.30 or more, from the standpoint of enhancing the chemicaldurability. From the standpoint of heightening the transparency aftercrystallization, ZrO₂/R₂O is preferably 0.80 or less, more preferably0.60 or less.

TiO₂ is a component capable of constituting crystal nuclei in acrystallization treatment and may be contained. Although TiO₂ is notessential, the content thereof, in cases when TiO₂ is contained, ispreferably 0.5% or more, more preferably 1% or more, still morepreferably 2% or more, especially preferably 3% or more, most preferably4% or more. Meanwhile, from the standpoint of inhibiting devitrificationduring melting, the content of TiO₂ is preferably 10% or less, morepreferably 8% or less, still more preferably 6% or less.

SnO₂ serves to accelerate the formation of crystal nuclei and may becontained. Although SnO₂ is not essential, the content thereof, in caseswhen SnO₂ is contained, is preferably 0.5% or more, more preferably 1%or more, still more preferably 1.5% or more, especially preferably 2% ormore. Meanwhile, from the standpoint of inhibiting devitrificationduring melting, the content of SnO₂ is preferably 6% or less, morepreferably 5% or less, still more preferably 4% or less, especiallypreferably 3% or less.

Y₂O₃ is a component which renders the chemically strengthened glass lessapt to scatter fragments upon breakage, and may be contained. Thecontent of Y₂O₃ is preferably 1% or more, more preferably 1.5% or more,still more preferably 2% or more, especially preferably 2.5% or more,extremely preferably 3% or more. Meanwhile, from the standpoint ofinhibiting devitrification during melting, the content of Y₂O₃ ispreferably 5% or less, more preferably 4% or less.

B₂O₃, although not essential, is a component which improves the chippingresistance of the glass for chemical strengthening or the chemicallystrengthened glass and improves the meltability, and may be contained.The content of B₂O₃, in cases when it is contained, is preferably 0.5%or more, more preferably 1% or more, still more preferably 2% or more,from the standpoint of improving the meltability. Meanwhile, in casewhere the content of B₂O₃ exceeds 5%, striae during melting or phaseseparation tends to occur to lower the quality of the glass for chemicalstrengthening. The content thereof is hence preferably 5% or less. Thecontent of B₂O₃ is more preferably 4% or less, still more preferably 3%or less, especially preferably 2% or less.

BaO, SrO, MgO, CaO, and ZnO are components improving the meltability ofthe glass and may be contained. In cases when these components arecontained, the sum of BaO, SrO, MgO, CaO, and ZnO, i.e.,BaO+SrO+MgO+CaO+ZnO, is preferably 0.5% or more, more preferably 1% ormore, still more preferably 1.5% or more, especially preferably 2% ormore. Meanwhile, the content of BaO+SrO+MgO+CaO+ZnO is preferably 8% orless, more preferably 6% or less, still more preferably 5% or less,especially preferably 4% or less, as ion exchange rate decreases.

Of those components, BaO, SrO, and ZnO may be contained in order toheighten the refractive index of the residual glass to a value close tothat of a precipitated-crystal phase and thereby improve a lighttransmittance of a glass ceramic and reduce a haze value. In this case,the total content of BaO+SrO+ZnO is preferably 0.3% or more, morepreferably 0.5% or more, still more preferably 0.7% or more, especiallypreferably 1% or more. Meanwhile, there are cases where these componentsreduce the ion exchange rate. From the standpoint of impartingsatisfactory chemical strengthening properties, BaO+SrO+ZnO ispreferably 2.5% or less, more preferably 2% or less, still morepreferably 1.7% or less, especially preferably 1.5% or less.

La₂O₃, Nb₂O₅, and Ta₂O₅ are all components which render the chemicallystrengthened glass less apt to scatter fragments upon breakage, and maybe contained in order to heighten the refractive index.

The total content of La₂O₃, Nb₂O₅, and Ta₂O₅, i.e., La₂O₃+Nb₂O₅+Ta₂O₅,is preferably 0.5% or more, more preferably 1% or more, still morepreferably 1.5% or more, especially preferably 2% or more. From thestandpoint of rendering the glass less apt to devitrify during melting,La₂O₃+Nb₂O₅+Ta₂O₅ is preferably 4% or less, more preferably 3% or less,still more preferably 2% or less, especially preferably 1% or less.

CeO₂ may be contained. CeO₂ has the effect of oxidizing the glass andsometimes inhibits coloration. The content of CeO₂, in cases when it iscontained, is preferably 0.03% or more, more preferably 0.05% or more,still more preferably 0.07% or more. In the case of using CeO₂ as anoxidizing agent, the content of CeO₂ is preferably 1.5% or less, morepreferably 1.0% or less, from the standpoint of heightening thetransparency.

In the case where the strengthened glass is to be used as a coloredglass, a coloring component may be added so long as the addition thereofdoes not inhibit the attainment of the desired chemical strengtheningproperties. Suitable examples of the coloring components include Co₃O₄,MnO₂, Fe₂O₃, NiO, CuO, Cr₂O₃, V₂O₅, Bi₂O₃, SeO₂, Er₂O₃, and Nd₂O₃.

The content of such coloring components is preferably 1% or less intotal. In the case where the glass is desired to have a highervisible-light transmittance, it is preferable that those components arenot substantially contained.

SO₃, a chloride, a fluoride, etc. may be suitably contained as arefining agent for use in glass melting. It is preferable that As₂O₃ isnot contained. In cases when Sb₂O₃ is contained, the content thereof ispreferably 0.3% or less, more preferably 0.1% or less. It is mostpreferable that no Sb₂O₃ is contained.

The present amorphous glass has a glass transition point Tg ofpreferably 390° C. or more, more preferably 410° C. or more, still morepreferably 420° C. or more. In cases when the glass transition point Tgthereof is high, stress relaxation is less apt to occur during chemicalstrengthening and, hence, high strength is apt to be obtained.Meanwhile, too high a Tg renders glass forming, etc. difficult.Consequently, the Tg thereof is preferably 650° C. or less, morepreferably 600° C. or less.

The present amorphous glass has a thermal expansion coefficient ofpreferably 90×10⁷/° C. or more, more preferably 100×10⁷/° C. or more,still more preferably 110×10⁷/° C. or more. Meanwhile, too high thermalexpansion coefficients make the glass prone to crack during forming.Consequently, the thermal expansion coefficient thereof is preferably150×10⁻⁷/° C. or less, more preferably 140×10⁻⁷/° C. or less. In casewhere there is a large difference in thermal expansion coefficientbetween the amorphous glass and lithium metasilicate crystals, crackingdue to the difference in thermal expansion coefficient is prone to occurduring crystallization.

In cases when the present amorphous glass is pulverized and examinedwith a differential scanning calorimeter, the glass gives a DSC curve inwhich the difference (Tc−Tg) between a glass transition point (Tg_(DSC))determined from the DSC curve and the temperature (Tc) corresponding toa crystallization peak appearing in the lowest-temperature range in theDSC curve is preferably 80° C. or more, more preferably 85° C. or more,still more preferably 90° C. or more, especially preferably 95° C. ormore. In cases when (Tc−Tg) is large, it is easy to process the glassceramic by bending with reheating, etc. (Tc−Tg) is preferably 150° C. orless, more preferably 140° C. or less.

FIG. 4 shows one example of DSC curves of an amorphous glass accordingto the present invention. There are cases where the Tg_(DSC) shown inFIG. 4 does not coincide with a glass transition point (Tg) determinedfrom a thermal expansion curve. In addition, since the glass is examinedafter having been pulverized, a large measurement error is prone tooccur. However, for evaluating a relationship with crystallization peaktemperature, it is appropriate to use the Tg_(DSC) determined by thesame DSC examination rather than the Tg determined from a thermalexpansion curve.

The present amorphous glass has a Young's modulus of preferably 75 GPaor more, more preferably 80 GPa or more, still more preferably 85 GPa ormore.

The Vickers hardness thereof is preferably 500 or more, more preferably550 or more.

<Production Method of Chemically Strengthened Glass>

The chemically strengthened glass of the present invention is producedby heat-treating the amorphous glass to obtain a glass ceramic and thensubjecting the obtained glass ceramic to a chemical strengtheningtreatment.

(Production of Amorphous Glass)

The amorphous glass can be produced, for example, by the followingmethod. Note that the following production method is an example ofproducing a sheet-shaped chemically strengthened glass.

Glass raw materials are mixed so as to obtain a glass having a preferredcomposition, and the mixture is heated and melted in a glass meltingfurnace. Thereafter, the molten glass is homogenized by bubbling,stirring, addition of a refining agent, etc., subsequently formed into aglass sheet with a given thickness by a known forming method, andannealed. Alternatively, use may be made of a method in which the moltenglass is formed into a block and the block is annealed and then cut intoa sheet form.

Examples of methods for forming a sheet-shaped glass include a floatprocess, a press process, a fusion process, and a downdraw process.Particularly in the case of producing a large-sized glass sheet, a floatprocess is preferred. In addition, continuous forming methods other thanthe float process, such as a fusion process and a downdraw process arealso preferred.

(Crystallization Treatment)

A glass ceramic is obtained by heat-treating the amorphous glassobtained by the procedure above.

The heat treatment is preferably a two-step heat treatment in which theamorphous glass is heated from room temperature to a first treatmenttemperature, held at this temperature for a certain time period, andthen held for a certain time period at a second treatment temperaturewhich is higher than the first treatment temperature.

In the case of performing the two-step heat treatment, the firsttreatment temperature is preferably in a temperature range where theglass composition has a high crystal nucleation rate and the secondtreatment temperature is preferably in a temperature range where theglass composition has a high crystal growth rate. It is preferable thatthe period of holding at the first treatment temperature is long enoughto produce a sufficient number of crystal nuclei. The production of alarge number of crystal nuclei results in crystals having small size toyield a glass ceramic having high transparency.

The first treatment temperature is, for example, 450-700° C. and thesecond treatment temperature is, for example, 600-800° C. The glass isheld at the first treatment temperature for 1 to 6 hours and then heldat the second treatment temperature for 1 to 6 hours.

The glass ceramic obtained by the procedure above is ground and polishedas necessary to form a glass ceramic sheet. In the case where the glassceramic sheet is to be cut into a given shape and size or to bechamfered, it is preferred to perform the cutting or chamfering beforegiving a chemical strengthening treatment to the glass ceramic sheet, asa compressive stress layer is formed also in the edge faces by the laterchemical strengthening treatment.

(Chemical Strengthening Treatment)

The chemical strengthening treatment is a treatment in which a glass isbrought into contact with a metal salt by, for example, a method ofimmersing the glass in a melt of the metal salt (e.g., potassiumnitrate) containing metal ions having a large ionic radius (typically,Na ions or K ions), thereby replacing metal ions having a small ionicradius (typically, Na ions or Li ions) contained in the glass with metalions having a large ionic radius (typically, Na ions or K ions forreplacing Li ions; K ions for replacing Na ions).

From the standpoint of heightening the rate of chemical strengtheningtreatment, it is preferred to use “Li—Na exchange” in which Li ions inthe glass are replaced with Na ions. From the standpoint of forminghigher compressive stress by ion exchange, it is preferred to use “Na—Kexchange” in which Na ions in the glass are replaced with K ions.

Examples of the molten salt for performing the chemical strengtheningtreatment include nitrates, sulfates, carbonates, and chlorides. Amongthese, examples of the nitrates include lithium nitrate, sodium nitrate,potassium nitrate, cesium nitrate, and silver nitrate. Examples of thesulfates include lithium sulfate, sodium sulfate, potassium sulfate,cesium sulfate, and silver sulfate. Examples of the carbonates includelithium carbonate, sodium carbonate, and potassium carbonate. Examplesof the chlorides include lithium chloride, sodium chloride, potassiumchloride, cesium chloride, and silver chloride. One of these moltensalts may be used alone, or two or more thereof may be used incombination.

As for the treatment conditions for the chemical strengtheningtreatment, time, temperature or the like may be appropriately selectedwhile taking account of the glass composition, the kind of molten salt,etc.

The present strengthened glass is preferably obtained, for example, bythe following two-step chemical strengthening treatment.

First, the present glass ceramic is immersed for about 0.1-10 hours inan Na-ion-containing metal salt (e.g., sodium nitrate) having atemperature of about 350-500° C. This causes ion exchange between Liions contained in the glass ceramic and Na ions contained in the metalsalt, and thus a compressive stress layer having a surface compressivestress value of, for example, 200 MPa or more and a maximum depth ofcompressive stress layer of, for example, 80 μm or more can be formed.

Next, the glass is immersed for about 0.1-10 hours in a K-ion-containingmetal salt (e.g., potassium nitrate) having a temperature of about350-500° C. This produces high compressive stress in the compressivestress layer formed in the previous treatment, in a portion, forexample, within a depth of about 10 μm. According to such a two-steptreatment, a favorable stress profile with a surface compressive stressvalue of 500 MPa or more is apt to be obtained.

Meanwhile, in a case where the surface compressive stress value exceeds1,000 MPa, it is difficult to obtain a large DOL while maintaining a lowCT. The surface compressive stress value is preferably 900 MPa or less,more preferably 700 MPa or less, still more preferably 600 MPa or less.

A method may be used in which the glass is first immersed in theNa-ion-containing metal salt, subsequently held in the air at 350-500°C. for 1-5 hours, and then immersed in the K-ion-containing metal salt.The holding temperature is preferably 425-475° C., more preferably440-460° C.

By holding the glass in the air at such a high temperature, the Na ionswhich have been introduced into the glass from the metal salt by thefirst treatment are thermally diffused in the glass to form a morefavorable stress profile and thereby heighten the drop strength toasphalt.

Use may also be made of a method in which the glass is immersed in theNa-ion-containing metal salt and is then immersed for 0.1-20 hours in ametal salt containing both Na ions and Li ions (e.g., a mixed salt ofsodium nitrate and lithium nitrate) having a temperature of 350-500° C.,instead of being held in the air.

By immersing the glass in the metal salt containing Na ions and Li ions,ion exchange is caused between Na ions contained in the glass and Liions contained in the metal salt to form a more favorable stress profileand thereby heighten the drop strength to asphalt.

From the standpoint of enhancing the drop strength to asphalt, thecompressive stress value CS50 at a depth of 50 m is preferably 100 MPaor more, more preferably 140 MPa or more, still more preferably 160 MPaor more.

In the case of performing such a two-step or three-step strengtheningtreatment, the total treatment time is preferably 10 hours or less, morepreferably 5 hours or less, still more preferably 3 hours or less, fromthe standpoint of production efficiency. Meanwhile, from the standpointof obtaining a desired stress profile, the total treatment time needs tobe 0.5 hours or more and is more preferably 1 hour or more.

The present strengthened glass is useful not only as thesemiconductor-supporting substrate which will be described later butalso as a cover glass for use in electronic appliances including mobiledevices such as cell phones and smartphones. The present strengthenedglass is useful also as the cover glasses of electronic appliances notintended to be portable, such as televisions, personal computers, andtouch panels, and as wall surfaces of elevators or wall surfaces ofhouses, buildings, and the like (entire-wall displays). Furthermore, thepresent strengthened glass is useful as building materials such aswindow glasses, table tops, interior materials for motor vehicles,airplanes, etc., and cover glasses for these, and as housings having acurved surface shape, etc.

Since the present strengthened glass has satisfactory high-frequencycharacteristics, it is suitable for use as the cover glasses ofappliances for high-frequency communication.

<Semiconductor-Supporting Substrate>

The semiconductor-supporting substrate (hereinafter also referred to as“supporting glass”) of the present invention is explained. Thesemiconductor-supporting substrate of the present invention includes theglass ceramic of the present invention. From the standpoint of attaininghigher strength, it is more preferable that the semiconductor-supportingsubstrate includes the strengthened glass of the present invention.

Since the present glass ceramic or the present strengthened glass has ahigh thermal expansion coefficient, these are suitable as a supportingsubstrate for fan-out packaging. In fan-out packaging, packages havingvarious average thermal expansion coefficients are formed depending onproportions of a semiconductor chip and a resin component. However,there are nowadays cases where molding resins are required to havehigher flowability to diminish filling failures and, hence, packageshaving a large resin component proportion and a high average thermalexpansion coefficient are frequently used.

FIG. 5A and FIG. 5B are examples of cross-sectional views of asupporting glass for laminating to semiconductor substrates. Thesupporting glass G1 shown in FIG. 5A is laminated to a semiconductorsubstrate 10 at a temperature of, for example, 200-400° C. through arelease layer 20 (which may function as a bonding layer), therebyobtaining the laminated substrate 30 shown in FIG. 5B. As thesemiconductor substrate 10, use is made, for example, of a full-sizesemiconductor wafer, a semiconductor chip, a substrate including asemiconductor chip molded with a resin, or a wafer on which elementshave been formed. The release layer 20 is, for example, a resinwithstanding temperatures of 200-400° C.

The present supporting substrate is used in applications where it islaminated to a semiconductor substrate. For example, the presentsupporting substrate is used as a supporting glass for fan-outwafer-level packaging, a supporting glass for image sensors, such asMEMSs, CMOSs, and CISs, in which a reduction in element size bywafer-level packaging is effective, a supporting glass havingthrough-holes (glass interposer; GIP), and a support glass forsemiconductor back grinding. The present supporting glass is especiallysuitable as a supporting glass for fan-out wafer-level and panel-levelpackaging.

FIG. 6 shows one example of cross-sectional views of a laminatedsubstrate in which the present supporting glass is used as a supportingsubstrate for fan-out wafer-level packaging.

In fan-out wafer-level packaging, semiconductor substrates 40 arelaminated to a supporting glass G2 at a temperature of, for example,200-400° C., through a release layer 50 of resin or the like (which mayfunction as a bonding layer). Furthermore, the semiconductor substrates40 are embedded with a resin 60, thereby obtaining a laminated substrate70. Thereafter, the release layer 50 is irradiated with a laser such asultraviolet light through the supporting glass G2, thereby removing thesupporting glass G2 from the semiconductor substrates 40 embedded in theresin 60. The supporting glass G2 is reusable. The semiconductorsubstrates 40 embedded in the resin 60 are wired with copper wires, etc.Wiring with copper wires or the like may be given beforehand to thesurface of the release layer. A substrate including semiconductor chipsembedded in a resin 60 may be used as a semiconductor substrate.

The present supporting substrate has a high light transmittance and,hence, a laser of high-energy visible light or a laser of ultravioletlight can be effectively utilized as the laser for use in the removal.

Examples

The present invention is described below by referring to Examples, butthe present invention is not limited thereto.

<Preparation and Evaluation of Amorphous Glasses>

Glass raw materials were mixed so as to result in each of the glasscompositions shown in mass % on an oxide basis in Tables 1 and 2, andweighed so as to yield 800 g of a glass. Subsequently, the mixed glassraw materials were put in a platinum crucible and this crucible wasintroduced into an electric furnace at 1,600° C., in which the mixturewas melted, degassed, and homogenized for about 5 hours.

The obtained molten glass was cast into a mold, held for 1 hour at atemperature of the glass transition point, and then cooled to roomtemperature at a rate of 0.5° C./min to obtain a glass block. Some ofthe obtained block was used to evaluate the amorphous glass for glasstransition point, thermal expansion coefficient, specific gravity,Young's modulus, refractive index, and Vickers hardness. The resultsthereof are shown in Tables 1 and 2. In the tables, each blank indicatesthat the property was not evaluated.

G1 to G22 and G26 to G33 are examples of amorphous glasses according tothe present invention, and G23 to G25 and G34 are comparative examples.G34 had suffered phase separation during the melting operation and wasunable to be evaluated.

(Glass Transition Point, Thermal Expansion Coefficient)

In accordance with JIS R1618:2002, a thermal expansion curve wasobtained using a thermal dilatometer (TD5000SA, manufactured by BrukerAXS GmbH) under the conditions of a heating rate of 10° C./min, and aglass transition point Tg [unit: ° C.] and a thermal expansioncoefficient were determined from the obtained thermal expansion curve.

(Specific Gravity)

The specific gravity was measured by the Archimedes method.

(Young's Modulus)

The Young's modulus was measured by an ultrasonic method.

(Vickers Hardness)

The Vickers hardness was measured by pressing an indenter under a loadof 100 gf for 15 seconds using a Shimadzu micro-Vickers hardness tester(HTMV-2, manufactured by Shimadzu Corporation).

(DSC Examination)

A glass was pulverized using an agate mortar, and about 80 mg of thepowder was put in a platinum cell and examined for DSC with adifferential scanning calorimeter (DSC3300SA, manufactured by BrukerGmbH) while being heated from room temperature to 1,100° C. at a heatingrate of 10° C./min. A glass transition point Tg_(DSC), a temperature Tccorresponding to a first crystallization peak, and the difference Tc−Tgbetween these temperatures were determined. FIG. 4 shows the results ofthe examination of G13.

(High-Frequency Characteristics)

The obtained glass block was processed into a sheet shape having athickness of 0.5 mm and examined with a network analyzer for relativepermittivity c and dielectric loss tangent tan δ at 10 GHz by asplit-post dielectric resonance method (SPDR method). The resultsthereof are shown in Table 1. After the crystallization treatment whichwill be described later, the glass was examined in the same manner; theresults of the examination made after the crystallization treatment areshown in Table 3.

TABLE 1 G1 G2 G3 G4 G5 G6 G7 G8 SiO₂  59.5  59.9  57.7  55.8  54.9  55.3 55.2  53.8 Al₂O₃  2.0  2.0  2.0  2.0  2.0  2.0  5.5  7.2 Li₂O  18.4 18.5  18.5  18.3  18.3  18.4  18.2  18.1 Na₂O  2.0  3.4  5.6  4.0  5.6 7.3  4.4  4.4 K₂O  2.0  0.0  0.0  4.1  3.4  0.9  0.8  0.8 MgO  0.0  0.0 0.0  0.0  0.0  0.0  0.0  0.0 CaO  0.0  0.0  0.0  0.0  0.0  0.0  0.0 0.0 P₂O₅  5.9  6.0  6.0  5.9  5.9  6.0  5.9  5.8 ZrO₂  10.1  10.1  10.1 10.0  10.0  10.1  10.0   9.9 Y₂O₃  0.0  0.0  0.0  0.0  0.0  0.0  0.0 0.0 TiO₂  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0 B₂O₃  0.0  0.0  0.0 0.0  0.0  0.0  0.0  0.0 SrO  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0SnO₂  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0 Specific gravity  2.52 2.53  2.53  2.54  2.54  2.54  2.55  2.55 Tg (° C.) 453 456 443 439 430428 450 460 Thermal expansion 125 127 131 137 141 144 131 127coefficient (×10⁻⁷/° C.) Tc (° C.) 589 586 576 563 564 Tg_(DSC) (° C.)470 469 452 460 467 Tc-Tg (° C.) 119 117 124 103  97 Young's modulus(GPa)  87  88  89  89  90  89  90  91 Vickers hardness 604 599 559 550561 551 540 568 Fracture toughness value  0.77 Relative permittivity 8.6 Dielectric loss tangent  0.017 G9 G10 G11 G12 G13 G14 G15 G16 SiO₂ 56.6  54.0  55.2  52.6  51.2  57.0  62.3  51.1 Al₂O₃  5.4  5.3  7.2 7.0  8.7  2.0  2.1  5.9 Li₂O  18.1  17.6  18.0  17.5  17.4  18.1  18.7 22.0 Na₂O  2.0  2.0  2.0  1.9  1.9  2.0  2.1  1.5 K₂O  2.0  1.9  2.0 1.9  1.9  2.0  2.1  1.5 MgO  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0 CaO 0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0 P₂O₅  5.9  5.7  5.8  5.7  5.6 5.8  6.1  5.9 ZrO₂   9.9   9.6   9.9   9.6   9.5  13.1   6.8  10.1 Y₂O₃ 0.0  3.9  0.0  3.9  3.9  0.0  0.0  2.0 TiO₂  0.0  0.0  0.0  0.0  0.0 0.0  0.0  0.0 B₂O₃  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0 SrO  0.0 0.0  0.0  0.0  0.0  0.0  0.0  0.0 SnO₂  0.0  0.0  0.0  0.0  0.0  0.0 0.0  0.0 Specific gravity  2.53  2.59  2.54  2.59  2.60  2.57  2.47 Tg(° C.) 469 470 467 468 471 465 448 Thermal expansion 122 123 122 120 124122 128 coefficient (×10−⁷/° C.) Tc (° C.) 593 592 592 571 571 Tg_(DSC)(° C.) 489 483 482 459 468 Tc-Tg (° C.) 104 109 110 112 103 Young'smodulus (GPa)  87  90  91  91  92  91  87 Vickers hardness 541 537 543631 621 627 555 Fracture toughness value  0.75 Relative permittivityDielectric loss tangent

TABLE 2 G17 G18 G19 G20 G21 G22 G23 G24 G25 G26 G27 G28 G29 G30 G31 G32G33 G34 SiO₂ 64.0 54.5 61.5 62.9 52.0 54.9 62.9 65.4 54.0 52.8 50.3 50.750.8 53.5 51.0 52.8 54.4 49.9 Al₂O₃ 5.9 2.0 2.0 2.0 1.9 2.0 22.4 22.418.0 8.7 8.5 12.0 12.1 8.7 8.5 8.8 8.9 2.0 Li₂O 10.0 18.4 18.4 13.0 17.516.9 4.3 4.3 0.0 17.5 17.0 17.2 17.3 17.4 17.0 17.6 17.8 28.0 Na₂O 2.02.0 0.1 2.0 1.9 5.0 2.0 2.0 13.0 1.9 1.9 1.9 2.6 0.5 0.5 1.9 2.0 2.0 K₂O2.0 2.0 2.0 2.0 1.9 5.6 0.0 0.0 2.3 0.0 0.0 1.9 0.8 0.8 0.8 1.9 2.0 2.0MgO 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.00.0 CaO 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 0.0 0.0 0.0 0.0 0.0 0.0 0.00.0 0.0 P₂O₅ 5.9 5.9 5.9 5.9 5.7 5.8 3.0 1.5 0.0 5.7 5.5 5.6 5.6 5.6 5.55.7 5.7 5.9 ZrO₂ 10.1 10.1 10.1 10.1 19.0 9.8 2.3 2.3 0.0 9.6 9.3 3.23.2 9.6 9.3 7.4 5.4 10.1 Y₂O₃ 0.0 5.0 0.0 2.0 0.0 0.0 0.0 0.0 0.0 3.97.5 7.6 7.6 3.9 7.5 3.9 3.9 0.0 TiO₂ 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.20.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 B₂O₃ 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.00.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 SrO 0.0 0.0 0.0 0.0 0.0 0.0 1.00.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 SnO₂ 0.0 0.0 0.0 0.0 0.0 0.02.1 2.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Specific 2.50 2.61 2.512.57 2.55 2.59 2.54 gravity Tg (° C.) 510 459 463 471 423 714 739 472.0488.0 461.0 478 470 450 Thermal 91 128 121 117 139 50 50 117 119 123 121123 124 expansion coefficient (×10⁻⁷/° C.) Tc (° C.) 740 627 593 627 946925 730 609 663 593 609 614 677 592 574 Tg_(DSC) (° C.) 535 473 481 501711 704 650 494 502 481 484 501 510 485 473 Tc-Tg (° C.) 205 154 112 126235 221 80 116 161 112 125 113 167 107 101 Young's 85 91 87 94 88 83 8394 95 91 92 94 93 93 90 modulus (GPa) Vickers 631 555 590 615 708 573575 567 577 570 566 570 558 hardness Fracture 0.80 0.71 toughness value

<Crystallization Treatment and Evaluation of Glass Ceramics>

The obtained glass blocks were each processed into 50 mm×50 mm×1.5 mm,and this processed glass was heat-treated under each of the sets ofconditions shown in Tables 3 and 4 to obtain a glass ceramic. Thesection “Crystallization conditions” in each table indicates nucleationtreatment conditions in the upper portion and crystal growth treatmentconditions in the lower portion. For example, in cases when a set ofconditions consists of “550° C.-2 h” in the upper portion and “730° C.-2h” in the lower portion, this means that the glass was held at 550° C.for 2 hours and then held at 730° C. for 2 hours. GC1 to GC17, GC19, andGC23 to GC35 are Working Examples, and GC18 and GC20 to GC22 areComparative Examples.

The obtained glass ceramics were each processed and mirror-polished toobtain a glass ceramic sheet having a thickness t of 0.7 mm. Rod-shapedsamples for examining thermal expansion coefficient were also prepared.Some of each remaining glass ceramic was pulverized and subjected toanalysis of precipitated crystals. The results of the evaluation of theglass ceramics are shown in Tables 3 to 5. The blanks indicate that theglasses were not evaluated.

(Visible-Light Transmittance, Y Value, Main Wavelength λd, ExcitationPurity Pe)

Each glass ceramic sheet was examined for transmittance within thewavelength range of 380-780 nm using a configuration including aspectrophotometer (LAMBDA950, manufactured by PerkinElmer, Inc.)equipped with an integrating-sphere unit (150-mm InGaAs Int. Sphere) asa detector. An arithmetic average of measured transmittance values wasobtained as an average transmittance [unit: %], which was taken as thevisible-light transmittance.

Moreover, tristimulus values X, Y, and Z for object in the XYZ colorsystem were calculated from the measured transmittance values todetermine an object color under illuminant C. The main wavelength λd andthe excitation purity Pe were determined therefrom.

(Haze Value)

Using a hazemeter (HZ-V3, manufactured by Suga Test Instruments Co.,Ltd.), a haze value [unit: %] was measured under an illuminant C.

(X-Ray Diffractometry: Precipitated Crystals and Degree ofCrystallinity)

Each glass ceramic was examined by powder X-ray diffractometry under thefollowing conditions to identify the precipitated crystals. Furthermore,the degree of crystallinity was calculated from the obtained diffractionintensities by a Rietveld method. Measurement apparatus: SmartLab,manufactured by Rigaku Corp.

X ray used: CuKα ray

Measurement range: 20=10°-80°

Speed: 10°/min

Step: 0.02°

The detected crystals are shown in the section of kinds of crystals inTables 3 and 4. In the tables, LS indicates lithium metasilicate, LDindicates lithium disilicate, PSP indicates β-spodumene, LP indicateslithiumphosphate, and spinel indicates spinel. Each degree ofcrystallinity is the sum of the degrees of crystallinity determined forthe respective kinds of crystals shown in Tables 3 to 5 by the Rietveldmethod.

(Crystal Size)

Glass ceramic GC1 was pulverized with an agate mortar and then sprinkledon a collodion film which had been hydrophilized. An extremely thinportion of the glass was examined with a transmission electronmicroscope (JEM-2010F, manufactured by JEOL Ltd.) to determine anaverage particle diameter (unit: nm) of the precipitated crystals. A TEMimage is shown in FIG. 7.

(Glass Transition Point, Thermal Expansion Coefficient, SpecificGravity, Young's Modulus, Vickers Hardness)

The properties were determined in the same manners as for the glasses ofbefore crystallization. Furthermore, the difference in Tg between beforeand after the crystallization was determined.

(Refractive Index)

Each glass ceramic was mirror-polished to 15 mm×15 mm×0.7 mm andexamined for refractive index by a V-block method using precisionrefractometer KPR-2000 (manufactured by Shimadzu Device Corp.).

TABLE 3 GC1 GC2 GC3 GC4 GC5 GC6 GC7 GC8 GC9 GC10 GC11 Glass G1 G2 G3 G4G5 G6 G7 G8 G9 G10 G11 composition Tg (° C.) 453 456 443 439 430 428 450460 469 470 467 before crystallization Heat 550-2 550-2 550-2 550-2550-2 550-2 550-2 550-2 550-2 550-2 550-2 treatment 730-2 710-2 710-2710-2 710-2 670-2 730-2 710-2 730-2 710-2 690-2 conditions (° C.-hr)Light 90.1 90.6 90.5 90.1 89.8 89.5 91.1 90.3 90.7 90.5 90.6transmittance (%) Y value 90.3 90.8 90.7 90.3 90 89.7 91.3 90.4 90.890.7 90.8 Main 573 573 572 572 573 574 571 574 571 574 572 wavelength λd(nm) Excitation 0.31 0.44 0.32 0.36 0.16 0.46 0.4 purity Pe Haze (%)0.08 0.08 0.09 0.07 0.11 0.11 0.07 0.08 0.07 0.08 0.08 Main LS LS LS LSLS LS LS crystals LP LS LP LS LP LS LP LS LP LP LP Crystal   20-40  20-40   20-40   20-40   20-40   20-40   20-40   20-40   20-40   20-40  20-40 size (nm) Degree of 40 40 40 40 40 40 40 40 40 40 40crystallinity or or or or or or or or or or or (%) less less less lessless less less less less less less Specific gravity 2.59 2.59 2.61 2.622.63 2.61 2.59 2.66 2.59 Tg (° C.) 627 587 595 585 601 578 624 624 586585 567 after crystallization ΔTg (° C.) 174 131 152 146 171 150 174 164117 115 100 Thermal 134 125 133 139 140 142 126 131 134 125 125expansion coefficient (×10⁻⁷/° C.) Young's 104 104 106 105 110 104 102104 102 modulus (GPa) Vickers 801 753 649 739 668 723 686 hardnessFracture 0.93 toughness value Refractive 1.5757 1.5764 1.5794 1.57991.5816 1.5825 1.5784 1.5759 1.5847 1.5763 index Relative 7.23permittivity Dielectric loss 0.007 tangent

TABLE 4 GC12 GC13 GC14 GC15 GC16 GC17 GC18 GC19 GC20 GC21 GC22 Glass G12G13 G14 G15 G1 G1 G1 G22 G23 G24 G25 composition Tg (° C.) 468 471 465448 453 453 453 423 714 739 650 before crystallization Heat 550-2 550-2550-2 550-2 550-2 550-2 550-2 550-2 750-4 750-4 650-2 treatment 710-2730-2 750-2 710-2 650-2 750-2 780-2 710-2 900-4 920-4 730-2 conditions(° C.-hr) Visible- 90.6 90.4 89.1 90.6 90.9 89.3 90.4 89.9 88.0 88.2light transmittance ( %) Y value 90.8 90.5 89.2 90.7 91.0 89.4 90.0 87.987.8 Main 570 573 574 576 576 573 576 578 582 wavelength λd (nm)Excitation 0.20 0.20 0.3 0.34 0.35 0.38 0.68 1.20 1.24 purity Pe Haze(%) 0.10 0.09 0.10 0.08 0.03 0.20 11.90 0.10 0.23 0.50 0.09 Main LS LSLS LS LS LS LS LS β SP β SP spinel crystals LP LP LP LD LP Crystal  20-40   20-40   20-40   20-40   20-40   20-40   30-80   20-40 120 1207 size (nm) Degree of 40 40 40 40 40 40 40 73 71 crystallinity or or oror or or or (%) less less less less less less less Tg (° C.) after 611610 601 638 612 872 902 crystallization ΔTg (° C.) 143 139 136 190 159Thermal 122 123 131 128 12 12 expansion coefficient (×10−7/° C.)Specific 2.66 2.66 2.64 2.54 2.58 2.59 2.63 2.48 2.48 gravity Young's105 105 109 103 101 105 107 105 87 90 81 modulus (GPa) Vickers 818 823696 723 788 786 730 783 732 hardness Fracture 0.91 0.83 0.72 toughnessvalue Refractive 1.5854 1.5769 1.5859 1.5639 1.5768 1.5232 1.5244 indexRelative 6.36 permittivity Dielectric 0.014 loss tangent

TABLE 5 GC23 GC24 GC25 GC26 GC27 GC28 GC29 GC30 GC31 GC32 GC33 GC34 GC35Glass G26 G27 G28 G29 G30 G31 G32 G33 G16 G17 G18 G19 G20 composition Tg(° C.) 472 488 464 467 469 473 470 451 510 459 463 beforecrystallization Heat 550-2 550-2 550-2 550-2 550-2 550-2 550-2 550-2550-2 550-2 550-2 550-2 550-2 treatment 710-2 690-2 730-2 710-2 690-2710-2 730-2 730-2 710-2 750-2 730-2 710-2 730-2 conditions (° C.-hr)Visible- 90.1 88.8 90.0 89.9 light transmittance (%) Y value Mainwavelength λd (nm) Excitation purity Pe Haze (%) 0.09 0.32 0.14 0.230.11 0.10 0.11 0.15 0.20 0.30 0.30 0.07 0.30 Main LS LS LS LS LS LS LSLS LS LS LS LS crystals LP LP LP LP LP LP LP LP LP LP Crystal   20-40  20-40   20-40   20-40   20-40   20-40   20-40   20-40   20-40   20-40  20-40   20-40   20-40 size (nm) Degree of 40 40 40 40 40 40 40 40 4040 40 40 40 crystallinity or or or or or or or or or or or or or (%)less less less less less less less less less less less less less Tg (°C.) 615 616 602 619 605 598 after crystallization ΔTg (° C.) 143 128 138152 135 147 Thermal 120 121 121 124 127 129 expansion coefficient(×10−7/° C.) Specific 2.71 2.64 2.60 2.52 2.68 2.57 gravity Young's 103104 103 105 103 104 104 104 91 108 101 modulus (GPa) Vickers 747 721 764610 755 730 722 hardness Fracture toughness value Refractive 1.58521.5936 1.5784 1.5713 index

GC18, in which lithium disilicate crystals had precipitated besideslithium metasilicate crystals, contained crystals having large particlediameters and had a large haze value and a poor appearance. GC20 andGC21, in which β-spodumene had precipitated, had glass transition pointsafter crystallization higher than 800° C. and had poor bendingprocessability.

<Chemical Strengthening Treatment and Evaluation of StrengthenedGlasses>

GC1 to GC16, GC19, GC22, and G1 which had not been crystallized wereeach subjected to a two-step chemical strengthening treatment consistingof 3-hours immersion in 450° C. sodium nitrate and subsequent 1-hourimmersion in 450° C. potassium nitrate. Thus, strengthened glasses SG1to SG19 were obtained. SG1 to SG16 are Working Examples, and SG17 toSG19 are Comparative Examples.

(Stress Profile)

Stress values were measured using surface stress meter FSM-6000,manufactured by Orihara Manufacturing Co., Ltd., and measuring deviceSLP-2000 utilizing scattered-light photoelasticity, manufactured byOrihara Manufacturing Co., Ltd., and thereby a compressive stress valueCS₀ [unit: MPa] on the glass surface, a compressive stress value CS₅₀[unit: MPa] at a depth of 50 μm, and a depth DOL [unit: μm] at which thecompressive stress value became zero were read out. The results thereofare shown in Tables 6 and 7.

A stress profile of SG13 is shown in FIG. 1.

TABLE 6 SG1 SG2 SG3 SG4 SG5 SG6 SG7 SG8 SG9 Glass for GC1 GC2 GC3 GC4GC5 GC6 GC7 GC8 GC9 strength- ening DOL 130 135 140 130 (μm) CS₀ 625 720750 490 515 629 800 900 700 (MPa) CS5₀ 195 155 150 (MPa)

TABLE 7 SG10 SG11 SG12 SG13 SG14 SG15 SG16 SG17 SG18 SG19 Glass forstrengthening GC10 GC11 GC12 GC13 GC14 GC15 GC16 G1 GC19 GC22 DOL (μm)124 140 122 126 125 120 50 CS₀ (MPa) 760 720 490 710 300 395 1000 CS₅₀(MPa) 230 209 214 222 179 0

SG17, which was obtained by chemically strengthening the glass which hasnot been subjected to crystallization, had a small value of CS₀ becausestress relaxation occurred during the strengthening treatment. SG18,which was obtained by chemically strengthening glass ceramic GC19 havinga high K₂O content, also had a small value of CS₀. SG19, which wasobtained by chemically strengthening glass ceramic GC22, which was aComparative Example containing no Li₂O, had a small value of DOL and wasless apt to have sufficient strength. It can be seen that the presentglass ceramic can obtain high strength through a chemical strengtheningtreatment.

While the present invention has been described in detail and withreference to specific embodiments thereof, it will be apparent to oneskilled in the art that various changes and modifications can be madetherein without departing from the spirit and scope thereof. Thisapplication is based on a Japanese patent application filed on Feb. 8,2019 (Application No. 2019-021896), the entire contents thereof beingincorporated herein by reference. All the references cited here areincorporated herein as a whole.

1. A glass ceramic having a visible-light transmittance of 85% or morein terms of a thickness of 0.7 mm, and a haze value of 1.0% or less interms of a thickness of 0.7 mm, and comprising, in mass % on an oxidebasis: 45-70% of SiO₂; 1-15% of Al₂O₃; and 10-25% of Li₂O.
 2. The glassceramic according to claim 1, having a content of K₂O of 5% or less inmass % on an oxide basis.
 3. The glass ceramic according to claim 1,comprising lithium metasilicate crystals.
 4. The glass ceramic accordingto claim 1, comprising lithiumphosphate crystals.
 5. The glass ceramicaccording to claim 3, wherein, in a case where lithium disilicatecrystals are contained, the lithium disilicate crystals have a crystalsize of 45 nm or less, the crystal size being determined using Scherrerequation from a width of an X-ray diffraction peak of the lithiumdisilicate crystals.
 6. The glass ceramic according to claim 1, having aglass transition point that differs by 200° C. or less from a glasstransition point of an amorphous glass having the same glass compositionas a glass composition of the glass ceramic.
 7. The glass ceramicaccording to claim 1, wherein the haze value is 0.4% or less in terms ofa thickness of 0.7 mm.
 8. A semiconductor-supporting substratecomprising the glass ceramic according to claim
 1. 9. A chemicallystrengthened glass having a compressive stress layer in a surfacethereof, the chemically strengthened glass being a glass ceramic thathas a visible-light transmittance of 85% or more in terms of a thicknessof 0.7 mm, and a haze value of 0.5% or less in terms of a thickness of0.7 mm, has a surface compressive stress value of 500 MPa or more and adepth of the compressive stress layer of 80 μm or more, and comprises,in mass % on an oxide basis: 45-70% of SiO₂; 1-15% of Al₂O₃; and 10-25%of Li₂O.
 10. The chemically strengthened glass according to claim 9,comprising lithium metasilicate crystals.
 11. The chemicallystrengthened glass according to claim 10, comprising lithiumphosphatecrystals.
 12. The chemically strengthened glass according to claim 9,having a compressive stress value of 100 MPa or more at a depth of 50 mfrom the surface.
 13. The chemically strengthened glass according toclaim 9, having an average thermal expansion coefficient at 50° C.-350°C. of 90×10⁻⁷/° C.-140×10⁻⁷/° C.
 14. The chemically strengthened glassaccording to claim 9, having a Vickers hardness of 600 or more.
 15. Asemiconductor-supporting substrate comprising the chemicallystrengthened glass according to claim
 9. 16. An electronic appliancecomprising the chemically strengthened glass according to claim 9.